Friction materials are well known to those skilled in the art. They find extensive used as brake linings, clutch facings, and the like. See, for example, U.S. Pat. Nos. 2,470,269 of Schaefer, 2,848,795 of Lowey, 3,019,514 of Bickelhaupt et al., 3,033,672 of Rejdak, 3,835,118 of Rhee, 4,391,641 of Lloyd, and 4,438,004 of Myers. The disclosure of each of these patents is hereby incorporated by reference into this specification.
The prior art processes for preparing friction materials generally involve the separate steps of forming a mixture of materials into a green body and then sintering the green body at elevated temperatures. These processes generally require expensive materials and the provision of heat for extended periods of time to effect the sintering. Furthermore, the prior art friction materials had friction properties which were not always satisfactory and/or which often degraded readily with temperature.
It is an object of this invention to provide a process for making friction materials which utilizes relatively inexpensive raw materials.
It is another object of this invention to provide an exothermic process for the preparation of friction materials.
It is another object of this invention to provide a one-step process in which the relatively inexpensive raw materials are formed and densified in situ to produce the shaped final product.
It is yet another object of this invention to provide a process for preparing a friction material with improved friction properties, such as improved friction coefficients, better self-lubrication, and increased wear resistance.
It is yet another object of this invention to provide a process for preparing a friction material with durable friction properties which do not degrade readily with heat.